Jan Zeman provides a telling appraisal applying official raw data of global surface temperatures to refute alarmist claims made in a recently trumpeted paper by Cowtan and Way. Authors’ claims of increased warming are controverted by compelling empirical evidence suggesting an emergent cooling trend instead.
Zeman’s analysis shows Cowtan and Way may have intentionally inserted a warming bias to fill a gap in data coverage of the tropical and polar regions. Principia Scientific International has pleasure in publishing Zeman’s damning full report below:
SIGNS OF COOLING
by Jan Zeman
Because there was a lot of publicity around the Cowtan and Way 2013 paper I decided to look into the issue, although, I note, it is not main concern of this article and it only makes suitable pretext to examine what is really going on with the global temperatures recently.
I was not much interested in their calculations and methods (since I’m not much interested in methods of data torture. Besides, they have already been scrutinized by much more knowledgeable people), but rather in the following questions:
Where did they obtain such data that would support a “two and a half times greater” rise of global temperature anomaly “trends starting in 1997 or 1998” in their “hybrid global reconstruction” when compared to the HadCRUT4 global temperature anomaly data-set, what such data really show and whether such data agree with other data or not?
The main rationale of their analysis seems to me to be that there is some missing coverage for the HadCRUT4 global temperature anomaly dataset “with the unsampled regions being concentrated at the poles and over Africa” and that it is the alleged reason why the HadCRUT4 dataset outcomes are purportedly biased, allegedly showing less warming than there is in reality. The main result of their analysis widely publicized was the bold red global trend. Because of this, the first thing I looked for was whether there actually are other data covering the regions and what trends one can find there.
Tropics
For starters, let’s see a comparison of HadCRUT4 and satellite lower troposphere data for the tropics.
(Note that I chose trend period exactly October-October to avoid potential disputes about the seasonal variations and cherry-picking. The data and calculations are available here.)
What we immediately see on the graph is that the HadCRUT4 trend 1997-present for the tropics (30S-30N) is flat (but it is slightly rising for the whole globe ~0.046°C per decade). We also see that both the UAH (the dataset Cowtan and Way likely used for their “reanalysis“ of the HadCRUT4 dataset) and the RSS satellite records show a descending temperature trend in the 1997-present period for the tropics. The only satellite data which show a rising temperature trend in the tropics is the UAH lower troposphere-land.